Ceramics



Patented Aug. 10, 1943 UNITED STATES PATIENT OFFICE John. W. Whittemore, Blacksburg, and Charles R. Oberfell, Lynchburg, Va., assignors to The Mead Corporation, Chillicothe, Ohio, a com.-

tion of Ohio No Drawing. Application March 15. 19:8, Serial No. 195,994 4 9 Claims. (01. 106-72) This invention relates to the production of articles'ifronr clays, and like earth materials; and, oneof the principal objects of the invention is to provide for the processing of such earth cles necessary in the subsequent processing and much loss is occasioned by the fact tha t the green articles have not had the necessary strength and that many defects have appeared therein during this necessary handling which materials to produce articles therefrom of quite caused future rejection. For example, in one superior and novel characteristics. case in actual commercial manufacture of build- Another object is to provide such processing ing brlck- -the formed wet brick are placed upon of "the clay,.or the like'earth material, that the drying platforms. After drying to the green 1 articles in thegreen condition have very sustate these brick are removed from the platperior characteristics which greatly increase the 10 forms, placed in the kiln and fired. The per-' yield in manufacture. centage of brick which develops cracks during Still another object is to provide such procdrying'so as to make them break up during haness'ing that the articles when fired to final form dling into the kiln or make'them fatally defecare ofquite superior strength, uniformity, and. tive in strength, etc., has been such that in order surface characteristics. 'to secure 480 good brick from each platformit Other objects and advantages will'be apwas necessary to put 512 wet brick thereon. parent from the description and the appended In order therefore to produce a given quantity claims. I Y I of satisfactory salable articleait is necessary to This application is a continuation in part of provide for and-add not only the additional numcopending application Serial Number 4,870" filed her of pieces which will probably berejected as February 4, 1935, now abandoned. a result of shrinkage, cracking, etc. during firing,

In the ordinary process for the manufacture but also a proportionately greater number ofof clay products, the clay. of the proper state of articles must be origin l y Prepared to r p ace fineness, -etc., is mixed with a quantity of water breakage, etc., occurring in the green state. The to give the desired plasticity and workability 26 present invention provides a simple processing and is then molded, or worked into the desired which gives characteristics of strength, etc.,.to shape or form. The formed article is then usuthe clay in its green state, which result in very ally dried-to a condition of strength which persuperior results at the end of the fired state, and mits of the further handling during the remainis therefore extremely important from a coming steps in manufacture. In this state the '30 mercial viewpoint because of reducing the partially dried articleis said to be in the green amount of wastage and increasing the proporcondition', and it is thereafter subjected to firing tion of salable articles from a given quantity of 1 or burning at relatively high temperature in a clay; and also because the accepted articles are kiln. themselves of increased strength, etc. There- Heretofore it has been universally accepted fore thereisimportant advantageintwo respects, 7 that considerable loss and waste of material namely, in decreasing losses, and in making the t would occur in the course of the manufacture or final product suitable for uses for which the ordiprocessing, so that to produce the desired numnary clay-articles having low strength properber of acceptable finished articles it was necesties'would not be usable. sary to sufferquite large losses of objects during 40 According to the present invention both of manufacture. These losses arose partly during these objects are attained-to a remarkable dethe firingoperation; but in addition, quite large gree and it is possible to greatly increase the losses have also been attributable to results arisstrength, uniformity and-desirable surface charing while the articles were in the green state oracteristics of clay products, both in the green being .dried to that condition. Generally, quite and in the fired states. The increase in strength evident cracks appear in a considerable per-' is almost unbelievably large, in some cases the centage of the formed articles during the process strength of the ultimate product being increased of drying making them useless even though they; many times. should not disintegrate before or during firing. .To secure this marked improvement in the Also many less evident cracks would appear dur-" o interim and final characteristics, the clay in the ing drying which would render the fired articles wet plastic state is processed by adding thereto unacceptable,-because of inferior appearance. a predetermined relatively small quantity of an r h, t There s also been large loss additive material containing a vegetable extract durihg'handling of the wet formed or green artihaving the extraordinary capacity of imparting these astonishing improvements. In the wet plastic state the clay contains in the neighborhood of approximately 20% to 30% moisture, depending upon the various characteristics of the clay itself, and is distinguished from the suspension or flowable slurry or slip condition such asis customary to be used in connection with the casting of ware. Very superior and satisfactory results in operation have been secured by adding to the clayin such wet plastic state small controlled amounts of the product known as chestnut extract, a product extracted from chestnut wood by leaching of chestnut wood chips. This product is well known and is available in considerable quantities at low cost, both in the dry and in the liquid form. It is a water soluble organic electrolyte obtained as a byproduct of the 7 paper industry,a typical analysis of the dry extract being as follows:

This extract is sold on the basis of its tannin content, the dry extract containing 65% tannin and the liquid extract being distributed on the Per cent Moistur 5.99 Total solids 94.01 Soluble so 92.64 Insolubles 1.34 Non-tannins 25.99 Tannins 66.65 Purity 74.91

basis of containing tannin, according to the 3:

testing method of the American Leather Chemists Association. This method of testing is merely empirical, and representsthe proportion of the extract which is absorbed. by hide powder.

The. highly complex organic structures of the various organic materials contained in chestnut extract, and the fact that many of these organic -maten'als are apparently unstable compounds,

has so far made it impossible to separate these various compounds, and to determine in exactly 40 The flocculating effect tends to coagulate the particles causing more continuous capillaries from the interior to the exterior of the mass, and this action facilitates the dispellingof occluded air and other gases that may be'adsorbed on the surface of the particles. It also facilitates the dispersion of the water from the interior to the exterior in the drying of the ware, which makes for easier and safer drying than when the clay is in adeflocculated condition and the capillaries are not as continuous in their arrangement from the interior of the piece to the surface. The flocculating action also has the effect of compacting the particles more closely together and of effecting more intimate interlocking thereof providing greater molecular attraction. In the fired state a glassy matrix is developed which gives superior adhesion, the glass forming more readily where the surfaces of the particles are in intimate contact, resulting in further improved strength. The density of the clay also increases inthe flocculated condition and less water is required to wet the clay to the wet plastic condition, such for instance that it will take an impression of the thumb. The reduced water content is also desirable as resulting in less drying and shrinking and such coagulation of the particles as results from flocculation also tends to eliminate unequal shrinkage with consequent reduction in local strains.

A proportion range which has been found to produce very satisfactory results is of the order of .1% to .25% of the dry extract ma- .teriaL- or a proportionate amount of the liquid extract having the same quantity of tannin material, based on the dry weight of the clay. Amaximuni proportionate improvement in the characteristics of the ware was secured with such small added-quantities of extract material, increase substantially beyond such range appearing to have less fiocculating effect, and

in some cases resulting in deflocculation with resultant reduction. in the ease and safety of drying. It is important in adding such small tallic salt. As with the case of the extract alone,

.with the character of the clay being used. For

instance, clays vary materially in organic content, in quantity of water required to produce a workable mix, in plasticity as well as in numerous other physical characteristics. A controlled small quantity of the extract, preferably including the desired proportion of salt therein, is added'to the clay prior to or while in the wet plastic condition during the processing. This proportion is so controlled with respect to a critical maximum value, as to bring about a flocculating action in the clay, resulting in making the clay quantities of additive. material that proper and homogeneous distribution thereof be secured throughout the plastic clay mass so that the additive material will be distributed and made eflective uniformly throughout the entire mass. For this purpose the plastic clay mass is therefore carefully worked at the time of the addition of the extract in suitable apparatus such as a pug mill, for 'suflicient length of time following addition of the extract to secure the desired uniformity of distribution.

The salt to be incorporated with the extract material is conveniently made up in solution -with the liquid extract, and the extract with the salt then incorporated with the wet plastic clay mass. The proportion of salt used with the extract may be varied from none at all to approximately equal or even somewhat greater quantities than the extract. As the quantity of salt is increased, the fired bricks show some tendency to become glazed or fused on their surface, the salt when present in sufllcient amount acting as a fluxing agent; accordingly the quantity 'of salt to be utilized is preferably limited to avoid the development of such fused condition. In commercial practice applicants have found it desirable to make up a mixture of tannin extract and saltin which the salt is more easily handled and more. readily worked. 7

portions are not critical, it is found that for widely vary most purposes this, or approximately this proportion range will give satisfactory results ior types of clays. and-that variation may. then be made in the quantity of the mixture or such materials which is incorporated in each case with the clay. The use of salt, is further desirable in conjunction with the chestnut extract as providing for the securing oi improved strength and other characteristics, inasmuch as the salt is less expensive than the extract, and a less expensive additive mixture having the increased effectiveness above described, even in the very small quantity range as indicated is thereby obtained.

The following is a specific example showing the results obtained by .the practicing of the present invention using a Virginia clay of secondary or alluvial deposit having a high content of fine grained free silica; and a low content of organic matter. It was found that the modulus of rupture of a natural clay of this character was 65 pounds per square inch when in the green state. The same clay in the fired condition had a modulus of rupture of 200 pounds per square inch. The addition to this clay of the mixture comprising 75% chestnut extract and 25% sodium chloride as above described, and in an amount corresponding to .2% or dry extract on the weight of the clay, re-

sulted in flocculating the clay and in an increase of the green dry modulus of rupture from 65 to 145 pounds per square inch, and in an increase of the fired strength from 200 to approximately 952 pounds per square inch. When 2% of the mixture was added, deflocculation or the clay particles occurred and the result-. 1

ing formed products were 01 impaired strength and other properties.

As another specific example, using a refractory clay, the' clay in its natural state had a green modulus of rupture of 231 pounds per square inch, and a fired modulus of rupture of 619 pounds per square inch. This clay was made down to a wet'plastic condition containing approximately .18% moisture, and 25% dry chestnut extract added thereto. This resulted in an increase in the green dry strength to 285 pounds per square inch, and in the fired strength to 735 pounds per square inch.

As another example,,a fine grained highly plastic clay suitable for the manufacture of saggers, the vfired color of which was cream, was utilized. This clay had a green modulus of rupteure of 315 pounds per square inch and a fired modulus oi rupture of ,2608 pounds per square inch. The addition to this clay of the mixture of chestnut extract and sodium chloride as above described in an amount corresponding to .125% dry tannin equivalent resulted in increasing the green modulus of rupture to approximately 4'70 pounds per square inch and the fired modulus of rupture to approximately 2960 pounds per square inch.

It is quite remarkable that these astonishing results in increase ,of the finished characteristicsand the strength of the finished product are best obtained with the addition of only a very small quantity of the additive material within the percentage range indicated. Consequently the invention is highly important in the fieldpf ceramics since these highly desirable characteristics are obtained with only a very small additional cost.

While the method and article herein described cojnstitute preferred embodiments of the invention, it is to be understood that the invention which is defined -matrix upon firing is not limited to this precise method-and product, and that changes out departing from the scope of the invention in the appended claims.

What is claimed is:

1. The method of incr the strength of. clay material which comprises adding therein while in a wet plastic state containing approximately 20% to 30% moisture a small controlled quantity of the order or .1% to .25% of an additive material in an amount such as to bring about a flocculating condition of particles of clay, said additive material comprising a mixture containing'a major proportion of chestnut extract as an essential ingredient andvoi the order of 20% to 40% common salt.

2. A clay product of the character described having greatly increased strength characteristics in both the green and the fired condition comprising clay material having an acid-reacting.

additive material uniformly incorporated and distributed therethrough while in a wet plastic condition in an amount or the order of .1% to 25% of the dry weight of the clay to effect flocculation thereof, said additive material including chestnut extract as an essential ingredient.

of the character described having greatly increased strength characteristics in both the green and the fired condition comprising clay material having an additive material uniformly 'incorporated and distributed therethrough while in a wet plastic condition containing of the order of 20% to 30% moisture in an amount of the order of .1% to 25% or the dry weight or the clay to efiect' flocculation of the clay particles, said additive material comprising a mixture containing a major proportion 01 chestnut extract and of the order of 20% to 40% common salt.

4. A clay product of the character described having greatly increased strength characteristics in both the green and the fired condition comprising clay material in a wet plastic condition having its particles in a flocculated condition with an acid-reacting additive material comprising chestnut extract as an essential ingredient uniformly incorporated and distributed threethrough in an amount of the order of .1% to .25% of the dry weight or the clay, said clay upon drying being in compact and dense condition with the clay particles interlocked inintimate relation providing for the development of a glassy 5. The method of providing a clay product having increased strength which comprises adding to the clay and thoroughly incorporatin therewith while taming approximately 20% to 30% moisture a controlled quantity of an acid-reacting additive material containing chestnut extract as an essential ingredient in an amount not exceeding a critical maximum'value up to approximately 25% based on the dry weight of the clay to secure a flocculating action of the clay particles in which dispersion of water and or occluded gases from the interior of the product is facilitated, and drying the clay product to provide a dense product in which the particles are in compact and intimately interlocked relation such that a glass matrix is developed upon firing.

6. The method of producing a molded clay product or the character described having increased strength in both the green and fired states which comprises placing the clay in a wet plastic condition containing approximately 20% may be made therein within a wet plastic condition con-' to 30% moisture, then causing a flocculation of the clay particles with resultant coagulation thereof to form substantially continuous capillary passages from the interior to the exterior of the moldedmass by incorporating and homogeneously distributing through the mass while in a said wet plastic state up to a critical maximum value of approximately 25% of an acid-reactin additive material containing chestnut extract as an essential ingredient, and thereafter forming and drying the molded clay product to provide a dense product in which the particles are in compact and intimately interlocked relation such that a glassy matrix is developed upon firing.

7. The method as defined in claim 6 in which the additive contains, in addition to said chestnut extract, approximately 20% to 40% common salt.

8. A clay composition of the character described adapted for use in molding to produce see product having increased strength characteristics in both the green and flred conditions comprising clay material. in a wet plastic state having its particles coagulated and forming substantially continuous capillary passages from the interior to the exterior of the mass by flocculation with an additive material,- said additive material comprising up to a critical maximum value of .25% and containing chestnut extract as an essential ingredient, said clay product upon drying being in compact and dense condition with the clay particles interlocked in intimate'relation providing for the development of a glassy matrix upon firing.

9. A product as defined in claim 8 in which said additive material contains in addition to said chestnut extract, approximately 20% to 40% common salt.

JOHN W. WHITIEMORE. CHARLES R. OBERFEIL.

cxmncn'm OF CORRECTION. 4 Patent m 2,526,729. August 10, 1915. Jolgn w. wnnmom; ET AL.

. It is hereby kgertifled that error appaars 1n the printed specificationof 1:116 abofi mmbqred patbnt requiring corraction as ro'il'ows; Page 5, first column, lin e,h5, for'.'.18$" read "18,1"; line 514., for rupteure' read --r'upture-; aid Second column, lines b.7448, foi' "threethfough", read --tharethrou@1--; and that the kind Lette'rs Patent should be read with thiicorredtion therein that the same may confdrm to the re cbrd of thb case in the Patent Office I I Sighpd and sealed. this 7th day of September, A. D. 1914.5.-

' Henry Var; Ar'sdale, (seal) Acting Commissioner of Patents. 

